NEW YORK (CNN) -- Jeff Walker says from as far back as he can remember, he always wanted to be a father.

Jeff Walker, with his two daughters, tried to adopt, but ultimately turned to surogacy to build a family.

"It was always something I knew, from the time I was a child." Just like his 3-year-old daughter, Elizabeth, who says she wants to be a mommy someday, Jeff says, "I knew I wanted to be a daddy."

Walker, a Manhattan music executive, says he and his partner had talked about adopting a baby years ago. But after three emotionally draining, failed attempts at adoption, they decided to turn to surrogacy. They contacted Circle Surrogacy, a Boston agency that specializes in gay clients. Their child was conceived with a donor egg, and then the embryo implanted in the surrogate, or carrier.

After Elizabeth was born, Walker and his partner separated. He then made a critical decision -- to become a dad again, single, and by choice.

"I realized my family, my two-dad family was going to look different than I thought it was going to look," he said. Without a partner, he would face even steeper challenges raising Elizabeth and a sibling alone. Walker says he gave the decision a lot of thought.

"That was the only part that was really controversial, because I do think there are a lot of challenges that single parents face, but at the same time I felt I was capable of handling those challenges," he said.

His second daughter, Alexandra, was born two years ago to the same surrogate, implanted with an egg from a different donor.

Walker, 45, is one of a growing number of single men -- both gay and straight -- who are opting to become fathers alone, with the help of gestational surrogacy.

Surrogacy experts say because the practice is not regulated, many surrogacy arrangements are handled privately by individuals. Precise figures are hard to come by, but experts say there's no doubt the United States is experiencing a surrogacy baby boom.

Celebrities like Ricky Martin and Clay Aiken announced this year they had had babies with the help of surrogates and the the Society for Assisted Reproductive Technology, representing scores of reproductive clinics, reports that the number of gestational surrogate births in the country quadrupled between 1996 and 2006. Watch more on the surrogacy boom »

Surrogacy experts say gestational surrogacy has increased steadily since the advent of in vitro fertilization in the early 1980s, because it provides an extra layer of emotional and legal protection for the client. The egg donor usually does not even know the client, and unlike the legally contentious "Baby M" case from the 1980s, the surrogate is not giving birth to her genetic child.

"It rises as an issue far less frequently with gestational surrogacy, because women never see it as their child to begin with," said John Weltman, president of Circle Surrogacy.

His agency, which expects more than 70 babies to be born in 2009, has seen a 50 percent growth in the number of single male clients over the past year.

Walker and other men are willing to pay well over $100,000 to have a baby through surrogacy -- the final cost depending on the number of IVF treatments necessary and how much is paid by insurance.

Circle is not the only major surrogacy provider experiencing a single-dad surge. At Growing Generations, a Los Angeles, California, agency that facilitates about 100 births a year, the number of single men seeking surrogates has doubled in the past three years, spokeswoman Erica Bowers said.

Although most of their single male clients are gay, surrogacy providers say a smaller but growing number are straight. Steven Harris, a New York malpractice and personal-injury attorney, says he gave up trying to get married when he realized his primary motive was to start a family.

Harris, 54, says he knew he made the right decision after 21-month old Ben was born.

"I thought getting married was the only way to go, because I did want a family. But having Ben, I feel complete now," Harris says.